With increasing legislative and environmental demands on middle distillate fuels, such as automotive gas oil (AGO) or industrial gas oil (IGO) and kerosene, it has been found increasingly difficult to meet the stringent cold flow properties, such as the cold filter plugging point (CFPP). In order to meet the most stringent legislative and environmental demands, Fischer-Tropsch derived middle distillates, with their inherent high quality will become more widely available within the next years. However, in spite of their outstanding quality, these middle distillates are known to suffer from poor cold flow properties due to high purity and high paraffin content, leading to the formation of wax crystals at relatively high temperatures. Furthermore, the addition of renewable fuels such as fatty acid methyl esters (FAME) and the high detergent dose rates associated therewith have been found to lead to a further decrease in the cold flow properties, specifically an increase in the cold filter plugging point. Accordingly, there is a need to be able to improve the response of middle distillate fuels to cold flow improvers.
EP-A-0308176 and EP-A-0255345 disclose the use of a mixture of n-paraffinic hydrocarbon waxes and a cold flow improver additive in mineral oil derived middle distillate fuel oils, e.g. heating oils and gas oil (diesel) fuels to give greater reductions in CFPP than the cold flow improver alone. However, the treat rates were rather high, even for mineral oil derived fuels, specifically if the wax content of the gas oil was taken into account.